Halogen-containing polymeric rubber compositions having improved scorch resistance

ABSTRACT

A halogen-containing polymeric rubber composition having improved scorch resistance, said composition comprising 100 parts by weight of a halogen-containing polymeric rubber having incorporated therein, as a antiscorching agent 0.1-5.0 parts by weight of at least one compound of the formula SH-R-(X)n WHEREIN R is selected from the group consisting of the aliphatic, alicyclic and aromatic hydrocarbon radicals, X is selected from the group consisting of amino, imino and carboxyl radical, and n is a number from 1 to 2. and 0.5 to five parts per weight of an amino-containing cross-linking agent.

llaite States atet Inventors Masaaki Inagami Yokohama-shi; Keiji Komuro, Tokyo, both of Japan Appl. No. 830,701 Filed June 5, 1969 Patented Nov. 30, I971 Assignee The Japanese Geon Company, Ltd.

Tokyo, Japan Priority June 12, 1968 Japan 43/39904 HALOGEN-CONTAINING POLYMERIC RUBBER COMPOSITIONS HAVING IMPROVED SCORCl-I RESISTANCE 4 Claims, 1 Drawing Fig.

US. Cl 260/453 R, 260/2 A, 260/45.85 R, 260/923 R, 260/94.7 S

Int. Cl ..C08d 11/04, C08f 45/60 Field of Search 260/4585,

45.9, 92.3, 94.7 S, 88.3 A, 2 EP, 2 A

Primary Examiner-Donald E. Czaja Assistant Examiner-V. P. Hoke A!!orne v-Sherman and Shalloway ABSTRACT: A halogen-containing polymeric rubber composition having improved scorch resistance, said composition comprising 100 parts by weight of a halogen-containing polymeric rubber having incorporated therein, as a antiscorching agent 0.1-5.0 parts by weight of at least one compound of the formula wherein R is selected from the group consisting of the aliphatic. alicyclic and aromatic hydrocarbon radicals, X is selected from the group consisting of amino, imino and carboxyl radical. and n is a number from 1 to 2. and 0.5 to five parts per weight of an amino-containing cross-linking agent.

PATENT EB time 1971 (Or he) (or T5) HALOGEN-CONTAINING POLYMERIC RUBBER COMPOSITIONS HAVING IMPROVED SCORCII RESISTANCE This invention relates to halogen-containing polymeric rubber compositions having improved scorch resistance. More particularly, the invention relates to halogen-containing polymeric rubber compositions having improved scorch resistance which are obtained by compounding a halogen-containing polymeric rubber with 0.1-5.0 parts by weight per 100 parts by weight of the rubber of at least one compound having the formula SHR-(X),, wherein R is either an aliphatic, alicyclic or aromatic hydrocarbon radical, X is either an amino, imino or carboxyl radical and n is either I or 2.

The halogen-containing polymeric rubber, e.g., polychloroprene, chlorinated butyl rubber, chlorinated polyethylene rubber, halogen-containing acrylic rubber, polyepichlorohydrin rubber and epichlorohydrin-olefin oxide copolymer rubber, have very excellent characteristics with respect to their chemical resistance, resistance to solvents and heat resistance on account of the halogen atoms contained therein. Hence, they are well-known as being commercially valuable rubbers.

These halogen-containing polymeric rubbers are crosslinked by means of an amino compound such as alkyl substituted thiourea and polyamines. However, when the halogen-containing polymers are cross-linked using these cross-linking agents, frequently premature cross-linking (also referred to as scorching) takes place to render the subsequent processing difficult.

Especially, under the circumstance where furnace black (which tends to become the cause of scorching) is used frequently, the prevention of this scorching has become a serious problem in the rubber industry.

While, methods of preventing the scorching of rubber, such as, spreading the rubber material out in a cool place, reducing the viscosity of the rubber material, reducing the amount compounded of the cross-linking agent and cross-linking accelerator, and using an improved cross-linking accelerator have been prepared, the procedure usually employed is that of kneading in an antiscorching agent in advance of cross-linking. As this antiscorching agent, an organic acid compound such as benzoic or phthalic acid is usually used. However, when these organic acid compounds are used as the antiscorching agent for halogen-containing polymeric rubbers whose cross-linking is carried out with amine compounds, the final rubber product that results after the cross-linking becomes one of inferior quality whose tensile stress (modulus) is low.

Accordingly, the object of the present invention is to provide a halogen-containing polymeric rubber composition whose scorch resistance is high without sacrificing the quality of the product.

The foregoing object of this invention is achieved by the incorporation in the halogen-containing polymeric rubbers as an antiscorching agent the compound of the formula SH-R L-- While the R in the formula SH-R-(X), can, as hereinbefore indicated, be a group selected from the broad group consisting of the aliphatic, alicyclic and aromatic hydrocarbon radicals, generally preferred is the lower aliphatic group, benzene nucleus or naphthalene nucleus.

As compounds comprehended by the foregoing formula, which are conveniently useable in the present invention, mention can be made of the following typical examples:

Z-mercaptoethylamine S H-CHzC H:NH:)

2-mercaptopropylamine S H-C HC HrNH2) lmlnoethylmercaptan (S H-G =NH) C Hz ortho-sminothlophenol SH- 2-amlno4-mercaptotoluene S HC 11;)

SH NH:

1 aamln.othlonaphthol U3 I NH: fl-aminothionaphthol l-mercapto'3-amlnocyclohexane EBB-Q thioglycollic acid (S HCHr-C O OH) thlosallcycllc acid S HQ and Specific examples of the halogen-containing polymeric rubbers to which the present invention can be applied include such as polychloroprene rubber, chlorinated butyl rubber, ethyl acrylate-chloroethylvinylether copolymer rubber (one class of acrylic rubber), fluorine-containing rubber, chlorinated polyethylene rubber, epichlorohydrin polymer rubber, epichlorohydrin-ethylene oxide copolymer rubber and epichlorohydrin-propylene oxide copolymer rubber.

A single class of the antiscorching agent can be used as well as a combination of two or more classes thereof. On the other hand, the amount of the antiscorching agent that is effectively used is 0.l-5.0 parts, and preferably 0.2-2.0 parts per parts of the rubber (weight basis; the parts given hereinafter are likewise all on a weight basis). An addition in an amount of less than 0.1 part does not bring about any conspicuous results, whereas an addition exceeding 5.0 parts is not practical since it is uneconomical though scorch preventive effects are brought about.

The incorporation of the antiscorching agent in the rubber may be carried out by any of the conventional mixing techniques. It is preferable that these antiscorching agents be incorporated into rubber before compounding of a cross-linking agent with it.

The halogen-containing polymeric rubber blend incorporated with 0.l-5.0 parts of the antiscorching agent has a scorch resistance which is markedly superior to that of the conventional blend containing an acid substance. Even the properties of the rubber obtained by effecting the cross-linking of this composition, are comparable to the rubber not containing the antiscorching agent, or even superior. The physical properties of the cross-linked rubber are further enhanced when carbon black is used as a reinforcing material.

The cross-linking agents suitable for cross-linking the halogen-containing polymeric rubbers include the aliphatic polyamines such as ethylene diamine, hexamethylcne diamine, diethylene triamine and triethylene tetramine, the aromatic polyamines such as p-phenylene diamine, m-phenylene diamine and cumene diamine, the polyamine carbamates such as ethylene diamine carbamate and hexamethylene diamine carbamate, the ketopolyamines and thioketopolyamines such as urea, biuret, thiourea, dibutylthiourea and trimethylthiourea, and further those consisting of a metal compound selected from the group consisting of aromatic and aliphatic carboxylates, carbonates, phosphates and oxides of the metals of groups IIA, [IE and [VB of the periodic table, used conjointly with either 2-mercaptoimidazolines or Z-mercaptorpyrimidines. These cross-linking agents are used either singly or in combinations of two or more, and they are usually used in an amount of 0.5-5.0 parts per 100 parts ofthe rubber.

Aside from the foregoing halogen-containing polymeric rubber, antiscorching agent and cross-linking agent, other compounding agents that are usually used in the conventional rubber blends such as, for example, cross-linking accelerators, stabilizers, age resisters, reinforcing agents and plasticizers may also be added to the rubber composition as required.

Next, the present invention will be more specifically described by means of the following examples and controls.

The Mooney scorch test was carried out in these examples and controls in accordance with the method ofJlS K-6300 except that the measuring temperature was changed to either 120 C. or 150 C. This Mooney scorch test consists in measuring with a Mooney viscometer the changes in the viscosity of the specimen rubber composition at the foregoing tempera tures as the cross-linking proceeds. The Mooney viscometer, as is well-known, is made up of a rotor, a hollow cylindrical dies which encloses the test piece and the rotor, a torque indicator, a heater and a temperature regulator. In conducting the measurement, a large rotor is used when the viscosity of the specimen rubber composition is relatively low and a small rotor when the viscosity is relatively high. The drawing is a graph explaining the test procedure.

As shown in FIG. 1, after the test is started, the Mooney viscosity value first declines with the passage of time and reaches a minimum value (Vm) and thereafter rises. When the large rotor has been used, the time t (min) required for the Mooney viscosity value to reach (V,,,+ after the start of the test is recorded. On the other hand, when the small rotor has been used, the time t (min) required for the Mooney viscosity value to reach (V,,,+ is recorded. As the values of t or t become greater, the scorch resistance is deemed to be higher. At the same time, the time t or t required for the Mooney viscosity value to reach (V,,,+ or (V,,,+ is also recorded. The value (t -t or t,,,-t;,) is a criterion which indicates the degree of the vulcanization rate.

EXAMPLES I-XlV AND CONTROLS T-lll Parts by Weight Polyepichlorohydrin rubber 100 Red lead 5 FEF grade carbon black 5 Variant amounts Z-Mcreaptoimidazoline Antiscorehing agent I Hydrin I00, a product of Goodrich Chemical Company, U.S.A.

'2 Asahi carbon 060 Japanese Industrial Standard. Further, the properties of the cross-linked rubber obtained by a cross-linking reaction for 30 minutes at 155 C. as well as the properties of this cross-linked rubber after ageing for 3 days at 150 C. in a test tube were 5 also tested in accordance with .118 K-630l. The results obtained in these tests are shown in table I.

In carrying out the examples given herein, the cross-linking reaction and ageing conditions identical to those given above were employed.

When control I and examples I-Vl, control II and examples VII-XI, and control III and examples XII, XIII and XIV are respectively compared, it can be seen that the antiscorching agent of the present invention demonstrates a pronounced scorch preventive effect without any adverse effects on the properties of the cross-linked rubber. 1

EXAMPLES xt-XVII AND CONTROL IV Part by weight Polychloroprene rubber 100 Red Lead 5 FEF grade car on black 50 Z-Mercaptoimidazoline 1.5 Antiscorching agent Variant amounts I Neoprene WRT produced by Showa Neoprene Company. Japan '2 Identical to those of example I.

The foregoing composition is kneaded together at below 100 C. using 3-inch rolls. A specimen is taken from this kneaded product and the Mooney scorch test is conducted at 120 C. in accordance with the .115 K-6300 method. Further, the cross-linked rubber is tested for its properties in accordance with the JIS K-6300 method. The results obtained in these tests are shown in table II.

4Q EXAMPLES XVIII-XIX AND CONTROL V Part by weight Ethylacrylatc-2-chloroethylvinyl ether copolymer rubber I00 Red lead 5 FEF grade carbon black $0 Z-Mercaptoimidazoline 1.5 Antiscorching agent Variant amounts '1 Hicar-420I produced by Goodrich Chemical Company. U.S.A.

'2 Identical to those of example I.

The foregoing blend is kneaded together at below C.

55 using 3-inch rolls. The Mooney scorch test at C. and the tests of the properties of the cross-linked rubber were conducted as in example I with the results shown in table Ill.

EXAMPLES XX-XXI AND CONTROL VI The operations as in example I are repeated with a blend of the foregoing composition. The results obtained are shown in 7 table IV.

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l Elaslene 402A produced by Showa Neo rene Company. Japan '2 Identical to those of example I.

Example I is repeated using a blend of the foregoing composition with the results shown in table V.

EXAMPLES XXIV-XX] AND CONTROLS VIll-Xll Pan by weight Polyepichlorohydrin rubher [00 Red lead 5 FEF grade carbon black 50 Z-Mercaptoimidazoline l.5 Antiscorching agent 0.5

I and '2 Identical to those of Example I.

Example I is repeated using a blend of the foregoing com- 30 position with the results shown in table Vl.

When comparisons are made between example XXlV and controls Vlll, IX and X, and between example XXV and controls Vlll, XI and Xll, it can be seen that the antiscorching agent according to the present invention not only demon- 35 strates a pronounced scorch resistance as compared with the EXAMPLES XXVI-XXVI] AND CONTROLS Xlll-XV Part by weight Polyepichlorohydrin rubber 'l Red lead 5 FEF grade carbon black 50 2-Mercaptoimidazoline LS Antiscorching agent 0.5

'l and '2 ldentieal to those of Example I.

The foregoing blend is submitted to the same operations as in example I with the results shown in table Vll.

When examples XXV] and XXVll are compared with controls Xlll, XlV and XV, it can be seen that while there are some among the conventional antiscorching agents which demonstrate some scorch resistance, that demonstrated by the antiscorching agent of the present invention is far greater and moreover there is the advantage that the properties of the cross-linked rubber are not adversely affected by the antiscorching agent of the present invention.

We claim:

1. A halogen-containing polymeric rubber composition having improved scorch resistance, which comprises per 100 parts by weight of a halogen-containing polymeric rubber selected from the group consisting of polychloroprene rubber, a chlorinated polyethylene rubber, a halogen-containing rubber. polyepichlorohydrin rubber,

other monofunctional compounds but also does not cause a substantial drop in the properties of the cross-linked rubber, and especially the modulus, thus indicating that it is of great value commercially.

acrylic SH-R-(X), wherein R is a member selected from the group consisting of lower aliphatic. cyclohexyl and aromatic TABLE VI Mooney sooreh test 120 C. Properties of cross-linked rubber Time required for rise of- Tensile Amount Minimum 5 Mooney 35 Mooney strength Elon- 100% Hardadded viscosity value units value units (kg/cm!) gation modulus ness Experiment Anti-scorching agent (phr.) (Mooney) (min.) (min (percent) g/ Control VIII Not incorporated 43. 8. 4 14. 9 157 290 71 73-70 gxartnplle XXIV Orthoaminothiophenol. 0. 5 40. 0 16. 4 30. 6 153 300 70 74-71 Ol'l [0 Z IX 1 Thiophenol- 0.5 43.5 10.7 17.4 140 330 59 72-69 X v Aniline 0. 5 44. 0 8.3 13. 7 141 320 60 74-72 gixmtnpllo XXV. 2-mercaptoethylaminm 0.5 44. 5 12. 5 17. 9 152 290 73 73-71 on to XI... Ethyl mercaptun .7 0.5 46.0 9. 7 15. 4 145 310 62 72-69 XIl.. Ethylominm. 0.5 43. 5 9. 8 14.1 141 320 57 70-67 TABLE VII Mooney scorch test 120 C. I

Properties of cross-linked rubber Time required for rise of- Tensile Amount Minimum 5 Mooney Mooney strength Elon- 100% Hardadded viscosit value units value units (kg/om!) gation modulus ness Experiment Anti-scorching agent (phr.) (Mooney min.) (min) (percent) (kg/em!) (J IS) Control XIII Not incorporated 45. 0 7. 5 12. 9 157 290 75 78-74 Example:

XXVI Orthoaminothiophenol. 0. 5 42. 5 17. 0 30. 5 153 300 71 76-75 {QgVII 2-mercaptoethylamine 0.5 47. 5 10.5 17.0 152 290 73 78-71 Ion ro XVI 1 Phthalic anhydride. 0.5 39. 5 8.7 15.7 150 320 66 75-7 X Benzoic acid 0.5 38.5 7.1 12.7 152 310 67 8- improved scorch resistance, which comprises per I00 parts by weight of polyepichlorohydrin rubber, 0.1-5.0 parts by weight of an aminothiophenol and 0.5-5.0 parts by weight of 2-mercaptoimidazoline.

4. An epichlorohydrin-ethylene oxide copolymer rubber composition having improved scorch resistance. which comprises per parts by weight of an epichlorohydrin-ethylene oxide copolymer rubber, 0.1-5.0 parts by weight of an aminothiophenol and 0.5-5.0 parts by weight of 2-mercaptoimidazoiine. 

2. and 0.5-5.0 parts by weight of an amino-containing cross-linking agent.
 2. The halogen-containing polymeric rubber composition of claim 1 wherein said amino-containing cross-linking agent is selected from hydrocarbyl aliphatic polyamines, hydrocarbyl aromatic polyamines, polyamine carbamates, keto-and thioketopolyamines, 2-mercaptoimidazolines and 2-mercaptopyrimidines.
 3. An epichlorohydrin polymer rubber composition having improved scorch resistance, which comprises per 100 parts by weight of polyepichlorohydrin rubber, 0.1-5.0 parts by weight of an aminothiophenol and 0.5-5.0 parts by weight of 2-mercaptoimidazoline.
 4. An epichlorohydrin-ethylene oxide copolymer rubber composition having improved scorch resistance, which comprises per 100 parts by weight of an epichlorohydrin-ethylene oxide copolymer rubber, 0.1-5.0 parts by weight of an aminothiophenol and 0.5-5.0 parts by weight of 2-mercaptoimidazoline. 